Drag the lens to move; right-click inside the lens to see the object picture without magnification.

The lenses are not thin.

The image is calculated on the assumption that the observer is far away from the lens and the object
picture is put under and close to the lens.

This applet is written in full accord with Snell's law of refraction. Therefore, the magnified/diminished
images seen perfectly match with the real cases. Click
here to see a comparsion.

If either the ratio h/D or the index of refraction (n) is too large, opague region(s) may appear at
the edge of the lens.

Indeed, this phenomenon is very common.

For instance, stand a transparent semi-circular block
upright with its flat surface facing upward. When viewed
from the top, the two ends of the upper flat surface
do not show any image of the bottom paper.
This is a phenomenon of the total internal reflection.
Practically, this can serve as an easy method of finding
the index of refraction of the block or a liquid filled
in a hemispherical transparent bowl.